NIO: shave off parts of System (#1658)
NIO: shave off parts of System (#1658)

This shaves off parts of System to reduce the noise when building to get
the Windows build more manageable.

Co-authored-by: Cory Benfield <e2b4f0650e369574e9b0029c3b3893634b6d4097@apple.com>
apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio